This invention relates to polyols containing one or more tertiary amine atoms, which are prepared in a Mannich condensation reaction to form a tertiary amine-containing intermediate which is subsequently alkoxylated.
Polyol precursor materials made by alkoxylating a Mannich condensation product (Mannich polyols) are known to be useful in preparing certain types of polyurethanes. Because these Mannich polyols contain tertiary nitrogen atoms, they are often auto-catalytic, i.e., are sufficiently reactive with isocyanate groups that they can be used to prepare polyurethanes with reduced levels of urethane catalysts, or even none at all. These Mannich polyols are typically of low equivalent weight, which makes them particularly suited to preparing rigid polyurethane foam, although their use as a crosslinker in semiflexible polyurethane foams is known as well. See U.S. Pat. No. 4,371,629.
The Mannich polyols used in polyurethane foams are prepared by alkoxylating a condensation product of phenol or a substituted phenol, formaldehyde, and diethanol amine. Such Mannich polyols are described, for example, in U.S. Pat. Nos. 3,297,597, 4,137,265 and 4,383,102, incorporated herein by reference. One problem with these Mannich polyols is that, due to the occurrence of side reactions in their preparation, they tend to be mixtures of single ring and multiring compounds rather than relatively pure materials. Worse, the extent to which multiring compounds are formed varies from batch to batch, so that successive batches of these Mannich polyols have varying properties. The presence of the multiring compounds causes the viscosity of the polyols to be higher than sometimes desired.
It would be desirable to provide a process for preparing Mannich polyols whereby the formation of multiring compounds is minimized or substantially eliminated. It would also be desirable to provide a process whereby the rate of alkoxylation of the Mannich condensate is increased.